1. Field of the Invention
The invention relates to an apparatus for chemical treatment of any selected portion of a subterranean well bore through the employment of two vertically spaced, inflatable packing elements.
2. Summary of the Prior Art
Vertically spaced, inflatable packing elements have been widely used to isolate a selected portion of a well bore for chemical treatment. Prior art apparatus for achieved circulation while the treatment apparatus was being run into the well by passing the circulation fluid through the entire tool. See U.S. Pat. No. 4,708,208. Furthermore, the required manipulation of valves in prior art treatment apparatus have generally required the utilization of set down weight. This renders impractical the use of coiled tubing as the fluid supply conduit upon which the treatment apparatus is run into well, since coiled tubing cannot apply any significant amount of set down weight.
It is also highly desirable that the portion of the well bore to be chemically treated not be saturated with fluids employed to effect the inflation or testing of the inflatable packing elements. In prior art apparatus, all of such setting and/or testing fluids contained in the coiled tubing were injected into the isolated well bore portion prior to the chemical treatment fluid ever reaching such portion. This, of course, is highly undesirable.
Lastly, prior art well treatment apparatus embodying a pair of vertically spaced, inflatable elements have not been designed so as to permit circulation during the retrieval of the entire apparatus from the well. There is a definitive need, therefore, for a well treatment apparatus employing axially spaced, inflatable packing elements that can be run into the well on an auxiliary tool, such as coiled tubing inserted through a pre-existing tubing string and is capable of performing all of the desirable functions, such as circulation during run-in, testing of the tool's pressure integrity after inflation of the packing elements, removal of the inflation and/or testing fluid from the tubing by forcing such fluid into a well bore above the uppermost inflatable element prior to initiating the introduction of chemical treatment fluid into the isolated portion of the well bore, deflation without set down weight to permit the inflatable packing elements to be repeatedly repositioned in the well bore, and lastly, provision for circulating while retrieving the treatment apparatus from the well bore.